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Issue A&A
Volume 500, Number 2, June III 2009
Page(s) 781 - 784
Section Galactic structure, stellar clusters, and populations
DOI 10.1051/0004-6361/200809404
Published online 01 April 2009

A&A 500, 781-784 (2009)
DOI: 10.1051/0004-6361/200809404

Potential-density pairs and vertical tilt of the stellar velocity ellipsoid

O. Bienaymé

Université de Strasbourg, CNRS, Observatoire Astronomique, France
    e-mail: bienayme@astro.u-strasbg.fr

Received 16 January 2008 / Accepted 9 March 2009

Abstract
We define new potential-density pairs and examine the impact of the potential flattening on the vertical velocity ellipsoid tilt, $\delta$. By means of numerical integrations and analytical calculations, we estimate $\delta$ in a variety of galactic potentials. We show that at 1 kpc above the Galactic plane at the solar radius, $\delta$ can differ by 5 degrees, depending on whether the dark matter halo is flat or spherical. This result excludes the possibility of an extremely flattened Galactic dark halo.


Key words: gravitation -- Galaxy: kinematics and dynamics -- Galaxy: structure -- stars: kinematics



© ESO 2009


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